The present invention relates to a window, in particular for mounting in an inclined roof surface, comprising a frame structure with top, bottom and side members and a relative to the frame structure openable, top-hung sash structure with an insulating pane enchased between top, bottom and side members of metal sheet profiles with a substantially L-shaped cross-section with a first wall portion covering a narrow edge zone of the exterior surface of the insulating pane and a second wall portion extending substantially in parallel with an edge surface of the insulating pane, a pivoting hinge provided at the top members of the frame and sash structures, the axis of which pivoting hinge is defined by engagement between a hook member integral with said second wall portion of the metal sheet profile of the sash top member and a hinge pin forming member of a fitting member connected with the frame top member, as well as securing means for maintaining the engagement between the hook member and the hinge pin forming member within a predetermined range of opening angle for the sash structure.
A window of this type is known from EP-A-0 410 369 and from international patent application No. WO93/11332. In these windows the entire sash structure and the fitting member connected with the frame top member are manufactured as extruded profiles. In the first-mentioned window the hinge members are constituted by a curved upward protrusion on the frame top member and a gasket placed in a downwards open groove in the sash top member and are permanently engaged without any possibility of disengagement, the movement of the sash top member being limited by adjacent parts of the frame top member or a superjacent sash profile. In the latter window the securing means comprise a block which is displaceably positioned in a groove in a sash side member and which may serve partly as an anchoring element for a locking member fastened in the frame structure in case of a not openable window, partly for releasable coupling with an operating arm in case of an openable window.
In consideration of the release of this coupling by manual operation, said block should normally be placed at a considerable distance from the pivoting hinge at the frame and sash top members, which on account of tolerances in the coupling members does not give full safety against unintentional release of the coupling. Furthermore, each release of the coupling, also within the opening angle range, will make it possible to dismount the sash relative to the frame.